This invention relates to an improved materials handling apparatus, and more specifically to lifting and dumping equipment of the type used with a front end loading refuse vehicle.
Front end loading refuse vehicles, as commonly constructed, have an enclosed body with an opening or door at the top for receiving refuse. A U-shaped lift arm is pivotally mounted on each side of the vehicle frame rearward of the cab, and these lift arms are pivoted between a lower and an upper position by hydraulic cylinders secured to the vehicle frame rearward of the lift arms. In the lower position, the back portion of each lift arm extends down rearward of the cab and the front portion extends down forward of the cab; and in the upper position, the front portion is above the body of the vehicle. A rotatable front tube or cross member extends across the vehicle between the front ends of these lift arms and may be rotated by hydraulic cylinders secured to the lift arms. A pair of fork arms are mounted on the front tube for engagement with a detachable refuse container. The fork arms are generally perpendicular to the tube whereby rotation of the front tube causes the fork arms to rotate in a generally vertical direction about the axis of the tube.
To empty a detachable container, the refuse vehicle is positioned directly in front of the container with the lift arms in their lower position and the fork means substantially horizontal. The container has sides spaced apart slightly less than the distance between the fork arms, and the sides of the container are provided with sleeves that can receive the fork arms. The vehicle is then moved forward to insert the fork arms into the sleeves; and then the lift arms, the front tube, and the fork arms are operated simultaneously to lift the refuse container above the body of the vehicle, maintain the container generally upright until it is above the body of the vehicle, and then invert the container to dump its contents into the body of the vehicle. To return the container to the ground, the movement of the lift arms, the front tube, and the fork arms is reversed. When the container is on the ground, the vehicle is moved backwards to disengage the fork arms from the container sleeves, and the vehicle can then proceed to the next container.
After disengaging a container, the fork arms are substantially horizontal and extend forward of the front ends of the lift arms. The vehicle can operate in the running mode with the form arms in this position; but, typically, when the vehicle is in transit, the fork arms are swung upwards in a vertical plane about the axis of the front tube. This is done by rotating the front tube by means of the hydraulic cylinders secured to the front portions of the lift arms and connected to the tube by levers, and this has the effect of increasing the vehicle's maneuverability by decreasing the effective length of the vehicle. However, before a second container can be engaged, the operator of the vehicle must realign the fork arms to a substantially horizontal position, and this horizontal realignment can consume a significant portion of the operator's time. Another disadvantage to pivoting the fork arm upwards about the axis of the front tube is that this may move the fork arms into a position where they may interfere with the vision of the operator of the vehicle. In addition, the fork arms cannot swing upwards far enough, simply by rotating the front tube, to eliminate their projection forward of the front ends of the lift arms, and this limits the extent to which the maneuverability of the vehicle can be increased by so moving the fork arms.